Remove grey vertical borders on edges of Emacs screen

[aidy lewis]

Hi,

I am using Emacs for Mac OSX. I have configured the .emacs file to present
a full screen without a scroll or tool bar.

(tool-bar-mode -1)
(set-frame-parameter nil 'fullscreen 'fullboth)
(scroll-bar-mode -1)

However, I have two thin grey vertical borders that appear on the edge of
the Emacs screen. Could anyone please tell me a function that will remove
these?

Thanks

Aidy